Based upon what you are saying, I personally think it's a bad idea that will ultimately end in disaster for your son, based upon his medical condition and his inability to earn a legitimate and substantial enough income to cover any deficiencies should a tenant tear the place up or another significant repair is needed such as a new roof or a new heater.

Just got a notice from my insurer to "Inspect and Repair, or Replace Roof" on my 4plex within 30 days.Huh, wha?

Arched shingled roofs.

But it's obvious cash flow beats equity any day of the week.You can get 30 yr fixes, and on down the line use cash flow to pay the mortgages off faster, but the 30yr gives you the option during lean times(loss of employment) new roof etc, to pay those out of cash flow, and not your own pocket.

If you were putting away an additional 5% for that (for the roof or you multiple boilers/furnaces and hot water heaters, etc.) then okay I'd buy it.So even though you are a contractor and will do the initial repairs and maintenance at cost I would still do it like you were paying someone else since at some point you might not want to or might not be able to do it.

From my short experience in the insurance industry (5 years), we had a guy that hit some one while drunk (2nd (alleged) DWI accident), another fell asleep at the wheel and hit some one head on, some one hit a full school bus that sent everyone to the hospital, some one flip a car and a passenger fell out of the sun roof and the car landed on them.

ALl major systems-hvac, roof, plumbing, elec, etc were all updated and/or replaced 8 years ago.

It went from a 3/1 to a 4/2, re-piped, re-tiled,electrical redone,new roof, kitchen updated, bathrooms updated; the works.

The roof might have to be replaced but we're not sure as my contractor doesn't have expertise in the roofing and he said that they were made of composite material that he never seen in residential houses.. usually seen in commercial building. we actually went to see this house on the rainy day and looks like there no water leaks into the house.

If you want assurances that certain items are good/bad/acceptable, you'd likely need to contact the individual trades that deal with each item (roof, foundation, electric, HVAC, etc.).